The traditional method of determining the weight of material loaded into a floating vessel, such as a barge, commonly known as "drafting" the vessel, involves the use of range rods or measuring tapes by personnel on the vessel. Usually, measurements are made manually at the corners of the deck to determine the distance from the deck to water level when the vessel is empty and after it has been loaded. The measurements thus obtained are then used in a known mathematical formula to calculate the weight of the payload in the floating vessel.
Inaccuracies arising in the traditional method of drafting vessels include the following:
(1) Because of wave action, the water level is never constant. PA1 (2) Because of water in the hold of the vessel or structural abnormality, the vessel undergoing loading is almost never level in the port-starboard or fore-aft planes before loading or after loading. PA1 (3) Visual drafting of a vessel is subject to variations in the depth perception of personnel and human error in the reading of range rods and measuring tapes, along with other miscalculations.
As a result of the above, large and costly errors are commonly made in calculating the payloads of barges and other vessels by the traditional method. Accordingly, it is the object of this invention to eliminate the deficiencies of the prior art by providing a method and a simple apparatus for automatically determining with high accuracy the weight of any payload introduced into a floating vessel at dockside by means of conventional loading equipment. The invention eliminates human error completely and eliminates or compensates for other error factors which are frequently present, including those enumerated above. Through the invention, the accurate drafting of floating vessels is rendered essentially automatic.